Knife grinder



J. A. LAPO INTE KNIFE GRINDER March 3, 1970 2 Sheets-Sheet 1 Filed June 26, 1967 FIG. I

INVENTOR Joseph Andrew LAPOINTE PA TENT AGENT Ma rch 3, 1970- J. A. LAPOINTE 3,493,002

KNIFE GRINDER Filed June 26. 19s? 2 Sheets-Sheet 2 IN VEN TOR Joseph Andrew LAPOINTE /1;ENT AGE:-

United States Patent 3,498,002 KNIFE GRINDER Joseph Andrew Lapointe, Pointe Claire, Quebec, Canada,

assignor to Domtar Limited, Montreal, Quebec, Canada, a company of Canada Filed June 26, 1967, Ser. No. 648,776 Int. Cl. B24b 3/36 US. Cl. 51-3 1 Claim ABSTRACT OF THE DISCLOSURE The present invention relates to a grinder for sharpening discrete wood wafer cutting knives having two cutting edges meeting at an angle and comprises a rotatable head upon which a plurality of such knives may be clamped, a pair of grinding stations in the path of travel of the knives, one station grinding in a plane substantially perpendicular to the axis of rotation of the head to sharpen one edge of each knife and the other station grinding at an angle to the axis to sharpen the other edge.

The present invention relates to a sharpener, more particularly to a grinder for sharpening knives and specially adapted to sharpen knives having a main cutting edge and an auxiliary cutting edge extending at an angle from one end of the main edge, i.e., knives used for cutting wood wafers from logs.

Prior to the present invention, knives having a main and an auxiliary cutting edge were ground on a reciprocating bed grinder with the knives moving in a straight line past a grinding station. Such machines are slow and cumbersome and must be very large if a multiplicity of knives are to be simultaneously processed. Also, such machines grind substantially straight surfaces on the knives.

It is the main object of the present invention to provide a new knife grinding machine which will relatively rapidly sharpen knives having two cutting edges.

It is a further object of the present invention to provide a grinding machine which will produce a spherical surface trailing one of the edges of the knife sharpened by the instant machine.

Broadly, the present invention comprises; a head rotatable about an axis, a plurality of knife mounting means on said head, at least two grinding stations at spaced positions in the path of rotation of said knife mounting means, one of said grinding stations having a grinding surface rotating in a plane substantially perpendicular to said axis and the other of said grinding stations having a grinding surface rotating in a plane extending at an acute angle to said axis.

Further features, objects and advantages of the present invention will be evident from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic plan view of the present invention with parts omitted for clarity.

FIG. 2 is a schematic view along the line 22 of FIG. 1.

FIG. 3 is a view along the line 3--3 of FIG. 1.

FIG. 4 is a view along the line 44 of FIG. 2.

FIG. 5 is a view substantially perpendicular to that shown in FIG. 4, and

FIG. 6 is a front view of one form of knife that may be sharpened with the present invention.

Before describing the apparatus of the present invention, reference will be made to FIG. 6 which shows one form of knife that may be sharpened using the instant invention. The illustrated knife 22 has a main edge 21 with a ground surface 23 extending rearwardly from 3,498,002 Patented Mar. 3, 1970 edge 21. Projecting at an angle from one end of the edge 21 is an auxiliary cutting edge 25. This auxiliary cutting edge 25 has a ground surface 27 which is in the form of a segment of a sphere extending rearwardly therefrom.

Referring to FIGS. 1 and 2, there is shown a device comprising a frame 10 supporting the various working parts of the apparatus. Mounted on the frame 1 0 is a main motor 12 which drives the knife mounting head 14 via a speed reducer 16 and a shaft 18. The head 14 is provided about its periphery with a plurality of knife clamps 20 which hold the knives 22 in proper position to engage the grinders. Each of the knife clamps 20 in the specific embodiment illustrated holds a knife 22 in position by means of shaft 32 having an eccentric section 34 rotatable therewith (see FIG. 3). The shaft 32 may be rotated via the knob 36 to lock or unlock each knife. Suitable guide means may be provided to facilitate accurate positioning of the knives in the holders.

There are three operating stations through which the knives travel as the head 14 is rotated. These stations are grinding stations 1 and 2 and the cooling station indicated at 3 (see FIG. 2).

.The cooling station is provided by a trough-like structure 38 having legs 40 and secured to the main frame 10 (see FIG. 2). This trough 38 is filled to a suitable level L with water or the like and the knives are dipped into and out of the water to cool same as the head rotates. Cooling may also be accomplished by directing cooling jets at the grinding areas of the wheels.

Grinding station 1 comprises a grinding motor 40 mounted on the frame 10 via bolts 42 extending through slots 44 which permit the motor 40 to move along a line substantially parallel to the axis of rotation of the head 14. Accurate adjustment of the grinder is obtained by an adjustment screw 46 which extends through and threadably engages bracket 48 and is coupled to the rear surface of the motor 40. By loosening the screws 42 and turning the adjustment screw 46 via a knob 50, axial adjustment of the motor and thereby the cup grinding wheel 52 secured to and rotatable with the motor shaft 54 is obtained. The grinder including motor 40 and grinding wheel 52 are then locked in position by tightening of the bolts 42.

The shaft 54 is substantially parallel to the shaft 18 and therefore the grinding surface 56 to the cup wheel 52 is substantially perpendicular to the shaft 18 and thus rotates in a plane that is substantially radial of the shaft 18. This orientation of the grinding surface 56 relative to the shaft 18 provides a simple means of accurately sharpening the main edge 21 of each of the knives 22.

Grinding station 2 is similar to station 1 but is set at an angle to the axis of the head 14 in position to sharpen the edge 25 on the knives. As shown, the grinder motor 60 at station 2 is mounted on the frame 10 by bolts 62 passing through slots 64 in the motor housing and threaded into the frame. The motor 60 and thus the grinder is adjustable by a bolt 66 which is threaded through frame bracket 68 and connected to the rear of motor 60. Rotation of bolt 66 via the knob 70 adjusts the position of the cup grinder wheel 72 connected to the grinder motor shaft 74 in a manner similar to that described above with reference to wheel 52.

The shaft 74 of motor 60 extends along a plane axial to the shaft 18 and is oriented to said shaft 18 at an acute angle. By arranging the shaft 74 in a plane axial to the shaft 18 the grinding surface 76 of cup wheel 72 engages the knife twice during each revolution of the head and thereby increases the grinding efficiency.

The angle of shaft 74 to the axis of rotation of the head 14 in the illustrated embodiment is not equal to the angle that the edge 25 projects from the edge 21 of the knife 22 because the mid-point of the edge 25 is not aligned with the shaft 74. If the said mid-point of edge 25 were in axial alignment with the shaft 74, this shaft would be at an angle to the axis of head 14 equal to the angle [between the edges 21 and 25 of the knife. In the illustrated embodiment the angle of the shaft of 74 to the axis of rotation of the head 14 is determined by projecting a line perpendicular to edge 25 from the midpoint of the edge 25 to intersect a projection of the axis of the head 14 and then drawing a line from said point of intersection to the shaft 74 and aligning the shaft 74 with said line.

Attention is directed to FIG. 3 which schematically illustrates sharpening of the main edge 21 of the knife 22. As can be seen the knife moves in the direction of the arrow 80 with the surface 23 trailing the edge 21 positioned in a plane 82 parallel to the direction of movement (i.e., plane 82 is radial to shaft 18). Also, the surface 56 of the grinding wheel 52 is mounted in a plane substantially radial to shafts 54 and 18. The grinding surface 56 is moved into position to grind the surface 23 thereby to sharpen the edge 21. As the knife moves past the grinding station 1 surface 56 acts at two locations and grinds the surface 23 in one direction as the knife moves toward the grinding station and in the other direction as the knife leaves the grinding station. The double action of the grinding surface 56 greatly increases the rate at which sharpening can be affected, Each knife 22 is, of course, accurately positioned relative to the plane 82 and is clamped in this position. Any suitable guide means may be used to so position the knives.

Auxiliary cutting edges 25 are sharpened as the knives traverse the grinding station 2. As above described the grinding wheel 72 and the edge 25 extend at angles to the axis of rotation of the head 14 and as a result the relative movement of wheel 72 and the knives produces a surface 27 on the knives trailing each] edge 25 which surfaces 27 are segments of spheres. Also the surface 76 of the grinding wheel 72 is a spherical zone (shown in cross section as are 84 in FIG. corresponding to the surface 27. Even the cutting edge 25 is not straight but extends along a slight arc. The shape of surface 27 permits the body of the knife trailing the edge 25 to be thicker and thus stronger and facilitates dissipation of heat.

The grinding action at station 2 is similar to that described above with respect to station 1 wherein the knives are ground in one direction as they approach the station and in another direction as they leave the station. At station 2 the surface 27 of the knife is first ground as the knife approaches the wheel, then the surface 27 passes into the hollow 86 in the grinding wheel and finally the surface 27 is ground a second time by movement of the grinder in a different direction than in the first grinding operation.

Applicants arrangement of the wheels 52 and 72 whereby a double grinding action is obtained not only speeds up the grinding operation but also eliminates any necessity for dressing of the grinding wheels. The grinders of the instant invention are self-dressing.

Applicant has thus described a new method and apparatus for grinding knives having main and auxiliary cutting edges, Modifications may be made to the disclosed embodiment without departing from the spirit of the invention as defined in the appended claim.

I claim:

-1. An apparatus for sharpening knives having a main cutting edge with a trailing ground surface and an auxili ary cutting edge having another trailing ground surface with said auxiliary cutting edge extending at an angle from one end of said main cutting edge, said apparatus comprising: a head rotatable about an axis of rotation, a plurality of knife mounting means mounted at a fixed radius from said axis of rotation on said head, said mounting means being adapted to fix each said main cutting edge and its trailing ground surface in a plane extending at an angle relative to said axis of rotation, a first grinding station and a second grinding station, said first grinding station having a grinding wheel the grinding surface of which is substantially parallel to said plane, means for relatively moving said grinding surface to said head whereby said grinding surface can grind said ground surface trailing said main edge and thereby sharpen said main edge, said second grinding station having a cupshaped grinding wheel, a spherical-shaped grinding zone in said cup-shaped grinding wheel, an axle, said cup wheel being mounted on said axle for rotation therewith, said axis of rotation of said axle and said axis of rotation of said head being laterally spaced and being in a common plane, the projection of said axis of rotation of said axle and of said head meeting at an acute angle, means mounting said cup wheel and said head for relative movement along a path axial of said axis of rotation of said axle, said spherical grinding zone being located in a position relative to said head whereby an auxiliary cutting edge on a knife mounted in said mounting means on said head when said head is rotated on its rotational axis would travel on an are from outside said cup wheel across said spherical zone into said cup wheel, across said spherical zone a second time and out of said cup wheel.

References Cited UNITED STATES PATENTS 1,212,552 1/1917 Pike 51-3 2,207,433 7/1940 Haswell.

2,548,277 4/1951 Whittlesey et a1. 5l-3 X FOREIGN PATENTS 1,608,144 1/1959 Germany.

JAMES L. JONES, JR., Primary Examiner Us X-R. 51 131 

